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Thread: java question regarding lilian calender

  1. #1
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    Default java question regarding lilian calender

    I have a program that asks a user for a date, then I compute how many days from 10/15/1582 to now that is. I want to take that number, and create a method that turns that number into a nice looking date such as "mm/dd/yyyy."

    Knowing how many days from 10/15/1582, how can I create a string that displays the date since then nicely?

    This is the method that takes the date and counts the number of days since 10/15/1582:
    public int lilian()
      {
        // Returns the Lilian Day Number of this date.
        // Precondition: This Date is a valid date after 10/14/1582.
        //
        // Computes the number of days between 1/1/0 and this date as if no calendar
        // reforms took place, then subtracts 578,100 so that October 15, 1582 is day 1. 
     
        final int subDays = 578100;  // number of calculated days from 1/1/0 to 10/14/1582
     
        int numDays = 0;
     
        // Add days in years.
        numDays = year * 365;
     
        // Add days in the months.
        if (month <= 2) 
          numDays = numDays + (month - 1) * 31;
        else 
          numDays = numDays + ((month - 1) * 31) - ((4 * (month-1) + 27) / 10);
     
        // Add days in the days.
        numDays = numDays + day;
     
        // Take care of leap years.
        numDays = numDays + (year / 4) - (year / 100) + (year / 400);
     
        // Handle special case of leap year but not yet leap day.
        if (month < 3) 
        {
            if ((year % 4) == 0)   numDays = numDays - 1;
            if ((year % 100) == 0) numDays = numDays + 1;
            if ((year % 400) == 0) numDays = numDays - 1;
          }
     
        // Subtract extra days up to 10/14/1582.
        numDays = numDays - subDays;
        return numDays;
      }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: java question regarding lilian calender

    Look at the Calendar class. It has lots of methods for working with dates.
    Also look at the DateFormat class

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    Default Re: java question regarding lilian calender

    If you have number of days, you can just do like;
    1. Divide the days into number of years, months and days.
    2. Add number of years into years, months into months and days into days (Remember to split date in three different variables and while adding don't forget to handle exceptions like days can't go more than 31, months not more than 12 and etc)
    Hope this will help you.
    Try this and if you got any problem, come up with your code.

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    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: java question regarding lilian calender

    Quote Originally Posted by Mr.777 View Post
    If you have number of days, you can just do like;
    1. Divide the days into number of years, months and days.
    2. Add number of years into years, months into months and days into days (Remember to split date in three different variables and while adding don't forget to handle exceptions like days can't go more than 31, months not more than 12 and etc)
    Hope this will help you.
    Try this and if you got any problem, come up with your code.
    This is certainly one way to do it, but Norm's suggestion handles all of that for you, as well as dealing with things like leap years, timezones, locales, etc.
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    Default Re: java question regarding lilian calender

    Quote Originally Posted by KevinWorkman View Post
    This is certainly one way to do it, but Norm's suggestion handles all of that for you, as well as dealing with things like leap years, timezones, locales, etc.
    Well, what Norm told was totally useless, as far as i know. The reason is he advised him to use the built in class and not encouraged him to write one.
    Well, i know that you will say, you must use built in modules in order to avoid effot. But you can not learn unless you do effort.

  6. #6
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: java question regarding lilian calender

    Quote Originally Posted by Mr.777 View Post
    Well, what Norm told was totally useless, as far as i know. The reason is he advised him to use the built in class and not encouraged him to write one.
    Well, i know that you will say, you must use built in modules in order to avoid effot. But you can not learn unless you do effort.
    That's pretty rude, and not true at all. Norm's suggestion is the way to go. I tried to be polite because you seem like a nice guy, but you're wrong here. I'm all for writing code the long way the first time around (using arrays instead of ArrayLists, etc), but there's a difference between working your way up and simply approaching a problem incorrectly.
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    Default Re: java question regarding lilian calender

    @KevinWorkman: I didn't mean to be rude. I actually told what was true. Don't you think, if we have a built in function and we use it. It's really easy to use than to make one, like that, to have a clear understanding and learning too.
    Anyways, i am sorry if you think, i am rude. I didn't actually mean that.
    My bad.

  8. #8
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    Default Re: java question regarding lilian calender

    Quote Originally Posted by Mr.777 View Post
    @KevinWorkman: I didn't mean to be rude.
    Saying "what Norm said was useless" is pretty rude, even if you do disagree with him. I disagree with you, but I'm not calling your post useless.

    Quote Originally Posted by Mr.777 View Post
    I actually told what was true.
    No, you didn't. Norm's answer stands as the correct one.

    Quote Originally Posted by Mr.777 View Post
    Don't you think, if we have a built in function and we use it. It's really easy to use than to make one, like that, to have a clear understanding and learning too.
    No, I don't. The Calendar, Date, and DateFormat classes exist for a reason. If somebody was using an array in a way that would be more suitable for an ArrayList, the correct answer is not to tell them to continue using arrays incorrectly so that they can understand them. The correct answer is to tell them to use an ArrayList. There's a reason we're using Java instead of C.

    And if this is for an introductory homework assignment (and using classes such as Calendar, Date, and DateFormat is disallowed), then it's the OP's responsibility to include that in the description. Until then, Norm's answer is correct.
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    Default Re: java question regarding lilian calender

    Alright. Now Peace out KevinWorkman and Thanks for advise. I am sorry Norm.

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